Packing tray and method for its production and use

ABSTRACT

There is described a packing tray ( 2 ) mainly of cardboard, paper, or a laminate, e.g. extruded, primarily containing these materials and in particular intended as sales packing for foodstuffs, e.g. meat, sliced meat or vegetables, poultry, fish, fruit, vegetables, salads, pasta, dishes for dinner, bakery and dairy products, which tray preferably has a rectangular shape with rounded corner parts ( 8 ), a mainly plane bottom ( 14 ) and sloping side walls ( 16 ) which at the top continue in an annular edge ( 12 ) approximately extending in parallel with the bottom ( 14 ), which tray ( 2 ) consists of one moulded item, the upper side of which consists of a gas- and/or diffusion-proof coating having such barrier abilities that a covering film or a dome-shaped, e.g. transparent, lid ( 18 ) may be connected gas-proof or diffusion-proof to the said annular edge by welding. There is also described a method for making and using, respectively, the packing tray.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The present invention relates to a packing tray substantially ofcardboard or, for example, an extruded laminate containing thesematerials.

Packing trays which utilize cardboard or extruded laminates thereof areused to a very large extent as sales packings for fresh foodstuffs ofalmost any kind, and most often the packing tray is provided with asimple wrapping of cheap plastic film. When speaking of meat, poultry,and fish, the shelf life of such fresh goods is only very short, andaccording to present practice and rules, the sales period for groundmeat is only one or two days. The sales period for sliced meat and fishis also only very few days, contributes to almost every supermarketnecessarily having its own butchering department which is often notprofitable at all based exclusively on turnover considerations.

GB-A-2 123 786 discloses a container in the form of a tray having a rimflange to which is heat-sealed a flexible first cover and a second coverof board material being attached to the first cover to strengthen thefilled and sealed container. The second cover, which is preferablyheat-sealed to the first, may have a window, and is removeable from thefirst cover without separation from the flange. The second cover maycarry required printing instead of, as in many cases, put the sealed tryinside a separate carton box simply to allow the outer carton to carrythe required printing. However, by this known packaging container thesealing between the very thin first cover and the rim is only leakproof.

SUMMARY OF THE INVENTION

With this background, the invention has the purpose of providing animproved packing tray which may be a contributing factor for increasing,by way of example, the sales period for fresh foodstuffs, such as meat,ground meat, sliced meat and vegetables, poultry, salads and fish, andalso may have other advantages.

The packing tray according to the invention has one press formed item,the upper side of which is a gas- and/or diffusion-proof coating havingbarrier abilities so that a covering film or a dome-shaped, e.g.transparent, lid may be connected in a gas-proof or diffusion-proofmanner to the annular edge by welding, with the annular edge at therounded corner parts being provided with bending lines, and the coatinghaving a minimum thickness sufficient to ensure a smoothing and meltingtogether of possible corrugations at the corner parts. By means ofsimple provisions there is hereby achieved a packing tray which isparticularly suited for packing fresh foodstuffs, such as meat, mincedmeat, sliced meat and vegetables, poultry and fish, fruit, vegetables,salads, pasta, dinner dishes, bakery and dairy products. The packingtray makes possible the final top sealing of the packing tray and itscontent with simultaneous scavenging with a protective gas with thepurpose of avoiding or reducing decomposition of the foodstuff, so thatthe keeping quality and hence the sales period of the foodstuffsconcerned may be prolonged considerably.

The barrier qualities of the surface coating of the packing trayaccording to the invention together with the covering film and/or thelids provide a gas- and diffusion-proof barrier with a high barriercharacteristic or with a low gas permeability. In practice, it is almostimpossible to have a coating or a film covering completely impermeableto diffusion of aqueous vapour. Besides, in connection with meat, thereis no real risk in practice of drying up as fresh meat gives offhumidity However, it is of great significance to minimize diffusion ofhumidity out of the packing tray according to the invention.

In a simple way the tray according to the invention ensures that a finaltop sealing with tightness is achieved along edge parts of the roundedcorner parts provided with bending lines that extend transversely to theedge parts. The thickness of the coating ensures, a smoothing of localunevennesses at corner parts because of the transversely directedbending lines, i.e. the thickness of the coating at the subsequent topsealing of the packing tray also contributes to improving the weldingand/or melting (adhesion) together at the corner parts.

Advantageously, the packing tray according to the invention may be thusdesigned so that the covering film is a peelable film, i.e. a film whichis exceptionally easy to remove from the annular edge of the packingtray.

With the purpose of making it very spacious, the packing tray accordingto the invention may advantageously be thus designed so that dome-shapedlids are used with a correspondingly designed, inverted tray, whichtrays are welded together edge to edge. In other words, the totalpacking consists of two identically shaped packing trays which arewelded in a gas-proof edge to edges manner.

The packing tray according to the invention may be thus designed assales packing in an advantageous way so that tray, lid and possiblepaper laminated extruded covering film are provided with printing.

Furthermore the packing tray according to the invention may be thusdesigned so that the tray is a single press formed item with the upperside of which between the cardbord and the upper weldable barriercoating provided with a susceptor coating. Thereby it is possible toachieve longer shelf life and at the same time a faster and more evencooking in a microwave oven.

The packing tray according to the invention may, by way of example, beused for prepared dinner dishes so that the tray is a single pressformed item having a substantially round, elliptical or oval tray shape.

Furthermore, the invention concerns a method for making a packing trayout of sheet- or roll-shaped material layer of a cardboard material,which is laminated, coated or provided with coating by extrusion withthe surface coating of material being weldable, which method punches thetray from blanks of material, the shape of which correspond to thepacking tray, that preferably before punching have bending linesembossed at corner parts of the blanks of material, and that thereafterare press formed by means of a press forming tool, which is preferably aheated press forming tool. Any possible projecting material is cut offthe annular edge of the finished packing trays.

The method according to the invention may advantageously be modified byusing a material with a thick surface coating, which at the subsequentpress forming by means of heat and/or friction, ensures a smoothing andmelting together of the bending lines at the corner parts of the annularedge at least.

The invention also concerns a method for using a packing tray, for salespacking for foodstuffs, where one or more food items, e.g. a recentlyslaughtered chicken, is placed on the tray. The method covers thefoodstuffs by a weldable, gas-proof film which is welded to the annularedge of the packing tray, preferably with simultaneous scavenging with aprotective gas.

An alternative method for using a packing tray is, for example for salespacking of foodstuffs, where one or more food items, e.g. a portion ofground flesh or meat, is placed on the tray, wherein the foodstuffs arecovered by means of a dome-shaped, transparent plastic lid which iswelded to the annular edge of the packing tray, preferably withsimultaneous scavenging with a protective gas.

A further alternative method for using a packing tray is, for examplefor sales packing for foodstuffs, e.g. prepared dinner dishes, where aportion of foodstuffs are placed on the tray, wherein the foodstuffs arecovered by means of a dome-shaped lid of a correspondingly shaped,inverted tray, so that the trays are welded together at the annularedge, preferably with simultaneous scavenging with a protective gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail in the following with thedrawing, on which:

FIG. 1 shows a top view of an embodiment of a packing according to theinvention,

FIG. 2 shows a longitudinal section of the packing tray shown in FIG. 1,and

FIG. 3 shows a transverse section of the packing tray shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The packing tray 2 has a shape known which is mainly rectangular withmutually parallel longer sides 4 and shorter sides 6 and with roundedcorner parts 8, each being designed with a large number of bending lines10. These bending lines 10 at the corner parts 8 also extend over anannular, outward bent edge 12 which is substantially in parallel with aplane bottom 14. A slightly outward/upward sloping side wall 16 extendsbetween the plane bottom and the annular edge 12. The bending lines 10at the corner parts 8 have the purpose of making easier press formingthe packing tray 2 out of a previously punched plane blank of materialwithout any breakage occurring in the blank which may be punched outfrom a sheet or roll shaped layer of material.

The packing tray 2 is made of cardboard, or preferably a laminatecontaining cardboard. The packing tray 2 is developed particularly foruse for fresh foodstuffs, e.g. meat, sliced meat or vegetables, poultry,fish, fruit, vegetables, salads, pasta, dinner dishes, bakery and dairyproducts and preferably there is used a laminated material of corematerial substantially of cardboard that either by coating or extrusionis provided with a suitable surface coating which at the side cominginto contact with the foodstuff is a gas-proof, weldable coating. Theexternal side or the underside of the packing tray or the material layermay optionally be impregnated in order to make the external side or theunderside less absorbing.

By means of the upper weldable coating of the tray 2, it becomes veryeasy to seal of the packing tray 2 at the top—when the foodstuff hasbeen placed on this—by means of a gas-proof, weldable plastic filmextending over the foodstuff e.g. a chicken, and which is welded to theannular edge 12 while scavenging with a protective gas, so that anefficiently sealed and presentable sales packing with exceptionally longkeeping qualities (shelf life) is formed.

The welding together may take place by means of a welding tool with awelding sole with a protruding edge so that welding together only takesplace along the edge, or there may be used a plane welding plate. Inorder to ensure that welding is made correctly and gas-proof also at thecorner parts 8 with the bending lines 10, welding soles or weldingplates with mutually co-operating projecting edges, grooves or lamellaemay be used.

In FIG. 2 showing a longitudinal section through the packing tray 2,there is furthermore shown with a stippled line that two identicallyshaped packing trays 2 welded together edge to edge may form a packingwith a relatively large capacity.

In FIG. 3 showing a cross section through the packing tray 2, there isfurthermore shown with a stippled line that the packing tray 2 may beprovided with a preferably rigidly dome-shaped lid 18 which, forexample, may be transparent and printed.

The surface coating of the packing tray may advantageously have severallayers, namely a lower hard cardboard layer and an upper soft weld layerwhich during the press forming process melts together by means of heator friction so that also the bending lines in the corner areas aresmoothed out with certainty and welded together in a gas-proof way.

For use as packing for prepared dinner dishes and other foodstuffs likepizzas and other dough items which are often cooked in a microwave oven,it may be suitable that at least the side of the cardboard or papermaterial constituting the inner side of the packing tray is coated witha susceptor coating of a hard plastic layer, e.g. PET or PEN, toward thecardboard or paper material, and which at the opposite side is a softweld coating. Thereby it is possible to achieve longer shelf life and atthe same time a faster and more even baking in the microwave oven. Itmay also be advantageous that the lid at the inner side is provided witha susceptor coating.

It should be noted that it is within the scope of the invention todesign the packing tray with any other form than the describedsubstantially rectangular shape. For example, the packing tray accordingto the invention may be designed with substantially circular orsubstantially elliptical shape. A possible alternative form of thepacking tray according to the invention may have multiple compartmentswhich may be arranged to be individually sealed with one of thecoverings, optionally including scavenging with protective gas (MAP orCAP) during the sealing procedure.

What is claimed is:
 1. A packing tray comprising: the packing trayincluding a plane bottom, sloping side walls extending upward from theplane bottom to an annular edge including rounded corner parts providedwith bending lines and extending approximately in parallel with thebottom and being formed from one of cardboard, paper, or a laminate ofcardboard or paper, a gas-proof weldable surface coating disposed on theplane bottom, sloping sidewalls and the annular edge of a thickness onthe annular edge sufficient to provide a top surface smoothing thebending lines to sealing with a tray top, the tray top comprising a gasproof layer which, upon packaging of foodstuffs therein, is connected ina gas-proof manner to the annular edge by adhesion to seal thefoodstuffs therein in a gas tight manner to an outside atmosphere.
 2. Apacking tray according to claim 1, wherein the tray top comprises acovering film which is peelable from the annular edge of the packingtray.
 3. A packing tray according to claim 1, wherein at least one ofthe tray and the tray top is provided with print.
 4. A packing trayaccording to claim 2, wherein at least one of the tray and the tray topis provided with print.
 5. A packing tray according to claim 1, whereinthe tray is press formed with an upper and inner side thereof betweenthe cardboard, paper or laminate of cardboard or paper and the surfacecoating comprising a susceptor coating.
 6. A packing tray according toclaim 1, wherein the tray is press formed and is substantially round. 7.A packing tray according to claim 1, wherein the tray is press formedand is a substantially elliptical or oval in shape.
 8. A method forproduction of a packing tray according to claim 1 wherein: the tray iscardboard provided from one of a sheet or roll with the surface coatingbeing provided by extrusion with blanks of cardboard of a shapecorresponding to the packing tray being punched out with the bendinglines embossed at corner parts of the blanks, which blanks thereafterare press formed into the tray by a press forming tool.
 9. A methodaccording to claim 8, wherein the surface coating by applied heat orfriction smooths and melts the bending lines at the corner parts of theannular edge.
 10. A use of a packing tray according to claim 1, as asales packing for foodstuffs, placed in the tray with the foodstuffsbeing covered by the tray top by welding to the annular edge of thepacking tray while simultaneous scavenging an inside of the tray with aprotective gas.